Lubricant



Patented July 15, 1941 UNITED N Drawing. Application May 10, 1938, Serial No. 207,071

11 Claims.

This invention relates to lubricants and the treatment of the same to improve the lubricating characteristics thereof, and is particularly applicable to mineral lubricating 'oils. Heretofore'it has been customary to build up the oiliness and film strength characteristics of lubricating. oils by the addition to such oils of minor proportions of various addition agents, of which may be mentioned the friction reducing agents such as fatty acids, fatty acid esters, castor oil, rape seed oil, Alox compounds (disclosed for example in U. S.

patent to Burwell No.' 1,863,004), and the acids,

esters, aldehydes and ketones of organic acids and mixtures thereof, nitriles and ketones, and the halogen and sulphur film strength increasing agents of which there are many on the market.

I have discovered that the lubricating characteristics of a lubricating oil may be improved by oxygenating or air treating the lubricating oil ,at a temperature substantially above normal room temperature. This oxygenation or air treatment may be accomplished by aerating the oil, for example. This aeration may be accomplished by any of a number of different methods,

.such as the rapid beating or agitation of the oil peratures above room temperatures will increase the lubricating characteristics of the oil, and

particularly the film strength thereof. By treating'the oil in this manner, the necessity of adding oiliness or film strength increasing agents STATES PATENT is greatly reduced or eliminated, and oils having the desired lubricating characteristics can in most cases be produced directly.

In accordance with this invention, I aerate the oil or cause an intimate contact or mixture of the oil and air, while at a temperature well above room temperature, for a periodof time which will produce approximately maximum increase in the lubricating characteristics of the oil. The increase in lubricating characteristics can be convenientlrmeasured by measuring the increase in film strength as determined by the testing of samples of the oxygenated or aerated oil on a simple lubricant tester. As soon as the treated oil shows that it possesses approximately the maximum film strength obtainable by air treatment, the aeration is stopped and the oil cooled back to approximately room temperature, which stops further oxygenation of the oil. Other oiliness and film strength increasing agents may also be added to the oil if desired, and if the air treatment does not give the desired results.

In further explanation of 'the nature of the invention, a number of practical examples, based on tests, will be given for illustrative purposes. The oil used in one series of tests, except as otherwise noted, was an S. A. E. No. gear oil made by blending 65% of No. 8' Pennsylvania Bright Stock with 35% of 230 viscosity (at F.), zero pour, 2 color Pennsylvania Neutral oil. The first group of tests on this blend of oils was made on the blend itself, and the second group of tests was made on the same blend of oil after air treatment or oxygenation in accordance with this invention, the aeration or air treatment occurring at a temperature of approximately C. and while the oil was being beaten or stirred at full speed with a double impeller, Sunbeam Mix Master or similar culinary heater for 2% minutes. The sample so mixed was a 2000 gram sample in an 8% inch kettle. This stirring or beating of the 1 heavy foaming thereof, and tended to into the body of the oil. sts which were made of the various oil herein described, were all run on 2. Tim- .cant tester, the test block being exam- ;he end of 1 minute, 3 minutes, and 10 an interval of 10 seconds being allowed :ase to start the machine, another interseconds in which to load the machine uniformly as possible, but this loading seconds is, of course, included each the total time under load. The results ests are indicated in the following table:

TABLE I.P61LM. .S'. A. E. 90 year base oil Oil as received Same, air treated i g iz Scarf Timken Timken Timken Scarf width width Scarf width Brin. div. film film film strength strength g? Strength 1 4. 33 13, 900 5. 12, 100 3 5. 33 11, 300 5. 00 100 10 6. 00 10, 100 6. 67 9, 070 1 4. 67 16, 200 5. 67 13, 300 3 6. 67 11, 300 7. 67 9, 870 10 7. 00 10, 800 7. 67 9, 870 1 6. 67 16, 000 5. 67 16, 000 3 Would not carry 18# lever load 6. 67 13, 600 8. 33 10, 800 10 '7. 33 (7 min.) 12, 300 9. 00 10, 000

cert last loading.

sults of these tests given above in Table indicate that the oil blend has increased nd film strength from the air treatment nation, which is comparable in many he results obtained by the addition to a lend of oils of 0.5% of a special oiliness agent which was made by the controlled of Pennsylvania Neutral Oil, followed lmination of acidic material, such as by ttion and washing, and of which Alox tone is an example. In Table I, the divisions refer to the average of the ths taken at each end and the center rith a Brinell microscope, the scale of '70 divisions, of which 63 divisions equal The Timken, film strength referred to I is the film strength calculated from the formula:

strength, lbs. per sq. in.= lever loadxm scarf width in Brin. div. K formula, K is a constant, equal to [984, which is the factor employed for z the average scarf width in a Brinell Mg inch scarf length) into square inches. en machine on which the tests were run iven from a 5 horsepower, alternating onstant speed motor. The motor may 1 the tests herein referred to was, of size in comparison to the power actuwhich makes speed variations during lerations virtually negligible. For all purposes, the 5 H. P. motor on such as a constant speed. Hence the speed ractically constant at about 810 R. P. 'Iimken tester for all ranges of load up nds. thod of improving the lubricating charof an oil is not limited to one par- !e of oil, as is demonstrated by the results of which are given below in vherein the oil tested was an S. A. E. lcosity, solventized naphthenic motor for the desired air treatment of the oil will deaeration at 150 pend upon the temperature at which the aeration or contact with the air takes place. Excellent results are obtained when the temperature of the oil during aeration is approximately 150 C.

Oils treated in this manner are particularly valuable in the manufacture of maximum film strength, gear lubricants. A lubricant made up of 95% of the Pennsylvania No. 90 gear oil base mentioned above, and 5% of chlorinated parafline (approximately 40% chlorine) heated to 150 C. and surface flashed but without such stirring as would incorporate much air into the oil, gave the tests shown under Oil 1 in Table III below; the same oil heated to 150 C., and stirred with a beater vigorously for 2 minutes (i. e. air treated), gave the test results under Oil 2 be-, low; the same oil reheated several times to 150 C. and air treated for a total of 30 minutes while at 150 C. gave the test results listed under Oil 65 3 below; of an oil of the same composition as Oil 1, plus 25% of "Oil 3 blended together, gave the test results listed under Oil .4 in Table III below; while an oil of exactly the same composition as Oil 4 but after air treatment or C. by means of an air jet for 20 seconds rather than high speed stirring, gave the test results listed under Oil 5" in Table III below. "Oil 6, referred to in Table III below, was made up of 95% of the air treated or aerated 5 oil of Table I, blended at C. with 5% of the same chlorinated paraffine. The results of tests on these various samples are listed in the following table:

ly that the air treatment or aeration of oil may be used on oil that also has added thereto, either before or after air treatment, any other addi- TABLE III Lever Time Oil 1 Oil 2 Oil 3 load, end Not air treated Air treated 2% min. Air treated 30 min. pounds Timken film str. Timken film str. Timken film str.

Minuies 10 Failed 340 sec 30,200# 27,20

Oil 6 Oil 4 011 5 Time, 75% like Oil 1" Air jet air treated" Q E f fi F fJ EZ Dumas end of- 25% of Oil 3" oil Timken film Z q g film p Timken film str. str.

Lever Oil 10 10 mg./100 gm. di

10 mg./100 gm. pyro- Oil 11 load Time, iso amyl amine, gallol-then air (was end ofthen air treated treated 15 mm. p 15 min. Timken Timken film str.

film str. I

Alinufes 10 Failed 300 sec Failed 390 sec.

These tests demonstrate that air treatment or aeration at temperatures well above room temperatures increases the film strength and other lubricating characteristics of an oil or gear lubricant, for example, to desirable limits. A comparison of the tests for Oils 1 and 2 above clearly establishes this fact, but it will be noted from the tests listed under Oil 3, that this air treatment or aeration can be carried or continued to such an extent that some of the desirable'properties are lost, that is, the final results are not as satisfactory as they are when the air treatment period is shorter. I have found, however, that if the oil is air treated for too long a period such as is illustrated under Oil 3, for example, the desired maximum lubricating characteristics may be restored to that overtreated oil by blending or incorporating therewith a proper quantity of non-air treated oil, as indicated under the results' of tests on Oil 4 in Table III. It is believed that oxygen will add on chemically to some parts or constituents of lubricating oils, particularly mineral oils, and it is my conclusion that air treatment of lubricatlng oil is a function of the air, presumably the oxygen of the air, that is chemically combined in the oil as shown by the results of the tests on Oil 5 listed in Table III. That the air treatment increases the property of the oil itself, and not that of any film strengthening agent which may be added, is demonstrated by the test results listed under Oil 6 in Table III, where the film strengthening agent received no air treatment whatever, and this indicates cleartion agent for increasing the lubricating characteristics of the oil, such as any suitable or desired film strengthening or friction reducing agents.

As a matter of convenience, the addition of a film strengthening agent of known properties to a small sample of a batch of air treated oil, followed by the testing of the blend, is an easy method of developing and testing an oil for maximum air treated properties in a large batch, which properties are rather difficult to determine in any other well known laboratory method. Of course it is preferable to air treat the oil approximately to the maximum film strength or increase in lubricating characteristics, rather than beyond that point, but free of other film strengthening agents, yet the maximum point is hard to determine by any other ordinary method.

It is recognized that even properly prepared gear lubricants apparently wear out in use, that is, they lose some of their lubricating characteristics, which loss is believed to be due to deterioration caused by exposure of the lubricant to pressure, temperatures above room temperature, entrained air, and metallic surfaces and particles, and other foreign matter introduced into the lubricant during use. A study of that problem of loss of desirable lubricating characteristics, particularly in ordinary gear lubricants during use, has led me to believe that the chief cause of the trouble or loss of lubricating characteristics was due to over-oxidation of the lubricant, which is similar to the efiects pointed out in Table III above with reference to Oil 3.

I have discovered that oxygen stabilizers added to the oil prevent such deterioration of the lubricants after maximum proper-ties have been developed in the lubricant. Apparently any of the agents which inhibit or stabilize oxidation may be used for this purpose, and I have indicated in Table III the results obtained when such an oxygen stabilizer was added to the air treated oil after maximum results have been obtained. Benzoic acid and di iso amyl amine are examples of oxygen stabilizers which have been successfully used for this purpose, and the results of tests using such stabilizers are listed under Oils 9 and in Table III. To demonstrate this effect more forcibly, I have listed under Oil 11 in Table III the results obtained after addition to the air treated oil of a minor proportion of pyrogallol which either accelerates oxygenation or deterioration of the oxygenated effect, that is, deterioration of the oxygenation of the oil, or adds an excess of oxygen material to the oil.

The tests, the results of which are tabulated in the foregoing .tables, except for Oil '7, were upon samples ranging in size from 1600 to 2000 rams and were all treated in 8 inch diameter kettles. For Oil 7, however, I used a 20 pound sample composed of 19 pounds of No. 90 ear base oil into which I blended 1 pound of the same chlorinated paraffine, and this mixture was air treated in a 13% inch diameter kettle for a total of 6 minutes at 150 C. "Oil '7 in Table III refers to this oil at this point. The results given in Table III for "Oil 8 were obtained after air treating 2000 grams of this same Oil 7 minutes longer at 115 C. in 8 inch diameter kettle. The results given for "Oil 9 on Table III were obtained by adding 10 mgs. of benzoic acid to 100 grams of this Oil '7 material, then air treating exactly like Oil 8. The results listed in Table III for Oil 10 were obtained by adding 10 mgs. of di iso amyl amine to 100 gram-s of the same "Oil 7 material, then air treating the same exactly like Oil 8'.

The results given in Table III for Oil 11 were obtained by adding 10 mgs. of pyrogallol to 100 grams of Oil 7 material, then air treating exactly like Oil 8. These tests clearly indicate marked retention of desired and better lubricating properties in the case of the benzoic acid sample. Similar results were obtained in the case of di iso amyl amine, although not quite so marked, and an acceleration of deterioration resulted When the pyrogallol was used. For the purposes of demonstration, equal amounts of the oxygen stabilizing materials and pyrogallol were used in these tests, but it will be understood that the invention is not limited to such amounts, because experience has demonstrated that the amount of one material required usually differs from that required when another material is used. Benzoic acid and di iso amyl amine belong to that class of materials which permits development of copper dish corrosion in the case of unstable gasoline and similar distillates, while pyrogallol is one of the most powerful inhibitors or preventors of such copper dish corrosion of unstable asoline.

I have found that various oiliness agents, such as fatty acids, fatty acid esters, castor oil, rape seed oil, Alox compounds, nitriles, ketones, and various other friction reducing agents may also be added to the air treated oil, either before or after air treatment, in order to lower the coefficient of friction of the blend and increase the lubricating characteristics of the product.

It will be understood that the hereinbefore described tests have been tabulated and described for the purpose of explaining the nature of the invention, and the manner in which it may be carried out, and that the invention contemplates considerable variation in the details, materials and proportions which have been herein described in connection with the listed examples, within the principle and scope of the invention, as expressed in the appended claims.

I claim as my invention:

1. The method of increasing a lubricating characteristic of an oil without material thickening thereof, which comprises bringing said oil while substantially above room temperature into intimate contact with air for a period of time sufiicient to obtain approximate maximum and possible film strength of a sample as determined by a lubricant tester, without material thickening of the oil, and then immediately stopping the intimate contact with air and cooling the oil.

2. The method of increasing a lubricating characteristic of an oil without material thickening thereof, which comprises bringing said oil while substantially above room temperature into intimate contact with air for a period of time dependent upon the temperature of the oil and the efiiciency of the intimate contact of the air with the oil, and until samples thereof at successive intervals during the heating, when tested on a lubricant tester,- show that approximately maximum film strength has been obtained, and before material thickening of the oil occurs, and then immediately cooling the oil.

3. The method of increasing a lubricating characteristic of an oil without material thickening thereof which comprises bringing the oil while at a temperature of approximately C. into intimate contact with air for the minimum period of time which will produce desired and possible increased film strength, without material thickening of the oil, and then immediately stopping the intimate contact with air, and adding thereto a minor amount of an oxidation inhibiting agent.

4. The method of increasing a lubricating characteristic of an oil without material thickening thereof, which comprises aerating the entire body of the oil at a temperature above room temperature, for the minimum period of time, dependent upon the increased temperature and the efliciency of aeration, which will impart to the oil a desired and possible increased film strength without material thickening of the oil, and then adding thereto an oxidation stabilizing agent to halt further oxidation.

5. The method of increasing a lubricating characteristic of mineral lubricating oil without material thickening thereof which comprises aerating the oil under controlled conditions at a temperature well above room temperature until an increased film strength of the oil is obtained and before material thickening of the oil occurs, and then blending with said oil a minor proportion of an addition agent for stabilizing oxidation of the oil to halt further oxidation.

6. The method of directly increasing the film strength of a mineral lubricating oil without material thickening thereof which consists in aerating all of the oil to be so increased, under controlled conditions at a temperature substantially above room temperature merely until the oil has the desired and possible increased film strength,

then adding to the oil a minor proportion of an oxygen stabilizing agent to halt further oxidation of the oil.

7. The method of increasing a lubricating characteristic of a mineral oil without material thickening thereof which comprises directly aerating the oil to be so increased, under controlled conditions at a temperature substantially above room temperatures until the oil possesses'a desired and possible increase in. film strength as determined by the testing of a sample on a lubricant tester, and before material thickening of the oil has occurred, and then cooling the oil back to room temperature, and adding a minor amount of an oxidation inhibitor to halt further oxidation.

8. The method of increasing a lubricating characteristic of a mineral oil without material thickening thereof which comprises oxygenating a portion of the oil under controlled conditions at a temperature substantially above room temperature, until a possible and desired degree of oxidation is obtained, and before material thickening of the oil occurs, thenvadding another portion of the oil with a lesser degree of oxygenation until a desired and possible increase in film strength of the mixture of oils is obtained, and adding to the mixture a minor amount of an oxidation inhibiting agent to halt further oxidation.

9. An improved lubricant comprising a mineral lubricating oil which has been separately aerated under controlled conditions at a temperature substantially above room temperature until a desired and possible increase in film strength is obtained, and before material thickening of the oil has occurred, and an added minor proportion of an oxygen stabilizing agent.

10. An improved lubricant comprising a mineral lubricating oil which has been separately aerated at a temperature substantially above room temperature until a desired and possible increase in film strength is obtained and an added minor proportion of an oxidation stabilizing agent of the type of benzoic acid and di iso amyl amine.

11. An improved lubricant comprising a mineral lubricating oil which has been separately aerated at a temperature substantially above room temperature until a desired and possible increase in film strength is'obtained, and before material thickening of the oil has been caused, an added minor proportion of a film strength increasing, addition agent, and an added minor proportion of an oxygen stabilizing agent.

' WILLIAM ALVAH SMITH. 

